The present invention relates to a catalyst system based on fulvene metal complexes as well as their use for the polymerisation of unsaturated compounds, in particular for the polymerisation and copolymerisation of olefins and/or dienes.
The use of cyclopentadienyl metal complexes, in particular the use of metallocene complexes in a mixture with activating co-catalysts, preferably alumoxanes (MAO), for the polymerisation of olefins and diolefins has been known for a long time (e.g. EP-A 129 368, 347 128, 347 129, 69 951, 351 392, 485 821, 485 823).
The metallocenes have proved to be highly effective, specific catalysts in the polymerisation, of in particular olefins. In order, therefore, to increase the activity, selectivity, control of the micro-structure, the molecular weights and the molecular weight distribution, a large number of novel metallocene catalysts or metallocene catalyst systems have been developed in recent years for the polymerisation of olefinic compounds.
The MAO-based catalyst systems described above have serious drawbacks, however, as will be explained in detail below. Firstly, aluminoxanes, in particular MAO, can be manufactured with high reproducibility neither in situ nor during preforming. MAO is a mixture of various aluminium alkyl-containing species, which are present in equilibrium with each other. The number and the structure of the aluminium compounds occurring in MAO is not defined precisely. The polymerisation of olefins with catalyst systems that contain MAO is therefore not always reproducible. Moreover, MAO is not storable over long periods and its composition changes under thermal stress. A major disadvantage is the high surplus of MAO which is required for the activation of metallocenes. The large MAO/metallocene ratio is an essential pre-requisite for obtaining high catalyst activities. This results in a critical process drawback, as the aluminium compound has to be separated from the polymer during the working up. MAO is furthermore a cost-determining factor. High MAO surpluses are uneconomic for industrial application.
In order to circumvent these drawbacks, alumoxane-free polymerisation catalysts have been developed in recent years. For example, Jordan et al report in J. Am. Chem. Soc., Vol. 108 (1986), 7410 on a cationic zirconocene-methyl complex which possesses tetraphenyl borate as counter-ion and polymerises ethylene into methylene chloride. In EP-A 277 003 and EP-A 277 004 ionic metallocenes are described which are produced by the reaction of metallocenes with ionising reagents. In EP-A 468 537 catalysts of ionic structure are described which are obtained by reacting metallocene-dialkyl compounds with tetrakis(pentafluorophenyl)boron compounds. The ionic metallocenes are suitable as catalysts for the polymerisation of olefins. A disadvantage is however the great sensitivity of the catalysts to impurities such as e.g. humidity and oxygen. Measures therefore have to taken during the performance of polymerisations to guarantee as great a purity of the monomers and solvents used as possible. This is very complicated technically and expensive.
In order to overcome these drawbacks, there are described in EP-A 427 697 and in WO 92/101723 processes for the polymerisation of olefins in which a combination of metallocene dichlorides with aluminium alkyls and tetrakis(pentafluorophenyl)boron compounds is used as a catalyst system. The aluminium alkyl compounds on the one hand serve as alkylation agents of the metallocene component and on the other function as scavengers in order to protect the active catalyst species against impurities.
The methods corresponding to the prior art for preparing the cationic metallocenes have the drawback, however, that the cationising reagents, e.g. tetrakis(pentafluorophenyl)boron compounds, are difficult to synthesise in some cases and their use is cost-intensive.
According to Bercaw et al., JACS (1972), 94, 1219, there is obtained by thermolysis of bis(xcex75-pentamethylcyclopentadienyl)titanium dimethyl the fulvene complex (xcex76-2,3,4,5-tetramethylcyclopentadienyl-1-methylene)(xcex75-pentamethylcyclopenta-dienyl)-titanium methyl. Nothing is known about the polymerisation activity of this complex. In T. J. Marks et al., JACS (1988), 110, 7701 the thermolysis of pentamethyl-cyclopentadienyl complexes of zirconium and hafnium is described. By thermolysis of bis(xcex75-pentamethyl-cyclopentadienyl)zirconium diphenyl the fulvene complex (xcex76-2,3,4,5-tetra-methylcyclopentadienyl-1-methylene)(xcex75-pentamethylcyclopentadienyl)-zirconium phenyl is obtained. This compound is not polymerisation-active on its own.
The object therefore existed of finding a catalyst system which prevents the above-mentioned drawbacks. In addition, processes based on aluminoxane-free metallocene systems were to be developed.
It has now been found, surprisingly, that catalyst systems based on fulvene metal complexes are particularly highly suitable for the objects set.
The present invention therefore provides a catalyst system consisting of
a) a fulvene metal complex with the formula 
xe2x80x83in which
M is a metal from the group IIIb, IVb, Vb, VIb or of the lanthanides or of the actinides of the Periodic Table of the Elements [N. N. Greenwood, A. Earnshaw, Chemie der Elemente, VCH 1990],
A signifies an optionally uni- or multi-bridged anionic ligand,
R1, R2, R3, R4, R5, R6, R7 are identical or different and stand for hydrogen, halogen, a cyano group, a C1 to C20 alkyl group, a C1 to C10 fluoroalkyl group, a C6 to C10 fluoroaryl group, a C1 to C10 alkoxy group, a C6 to C20 aryl group, a C6 to C10 aryloxy group, a C2 to C10 alkenyl group, a C7 to C40 arylalkyl group, a C7 to C40 alkylaryl group, a C8 to C40 arylalkenyl group, a C2 to C10 alkinyl group, a silyl group optionally substituted by C1 to C10 hydrocarbon groups or
R1, R2, R3, R4, R5, R6, R7 form respectively together with the atoms linking them one or more aliphatic or aromatic ring systems, which can contain one or more hetero atoms (O,N,S) and have 5 to 10 carbon atoms,
m signifies 0, 1, 2 or 3 and
k is 1, 2 or 3 and the sum of m+k comes to 1 to 5 as a function of the oxidation state of M and
b) an aluminoxane- and boron-free Lewis acid suitable for activating the metal complex a), wherein the molar ratio of component a) to component b) lies in the range of 1:0.1 to 1:10000, preferably 1:1 to 1:1000.
The synthesis of the fulvene metal complexes of formula (I) is known and described for example in T. J. Marks et al., Organometallics 1987, 6, 232-241.
The present invention further provides a process for producing a catalyst system, characterised in that a mixture of an aluminoxane- and boron-free Lewis acid suitable for activation and a metal complex of formula (II) 
in which
M, A, R1 to R7 have the signification indicated according to claim 1, and
X stands for hydrogen, halogen, a C1 to C30 alkyl group, a C6 to C10 aryl group, a C2 to C10 alkenyl group, a C7 to C40 arylalkyl group, a C7 to C40 alkylaryl group, a C8 to C40 arylalkenyl group, a C2 to C10 alkinyl group, an optionally substituted silyl group,
is treated thermally in a suitable reaction medium.
The thermal treatment takes place in the temperature range from 60xc2x0 C. to 250xc2x0 C., preferably from 90xc2x0 C. to 150xc2x0 C. The duration of the thermal treatment lies in the range from 1 minute to 20 hours, preferably in the range from 15 minutes to 120 minutes. Suitable reaction media are for example aromatic hydrocarbons, such as benzene or toluene, or aliphatic hydrocarbons, such as hexane, heptane, octane, cyclohexane or mixtures of the various hydrocarbons. The thermal treatment is not carried out in the presence of an olefin or diolefin. The molar ratio of the Lewis acid to the metal complex of formula (II) lies in the range from 1:0.1 to 1:10000, preferably 1:1 to 1:1000.
There are considered as fulvene metal complexes of formula (I) in particular those in which
M is a metal of the group IVb, Vb or of the lanthanides of the Periodic Table of the Elements,
A is an allyl group of the formula C3R65, where R6 has the same signification as R1 to R5 in formula (I),
a halide, F, Cl, Br, I,
a sulfonate of the formula O3SR6,
an amide of the formula NR62,
a pyrazolate of the formula N2C3R73 with R7 for hydrogen or a C1-C10 alkyl group,
a pyrazolyl borate of the formula R6B(N2C3R73)3,
an alcoholate or phenolate of the formula OR6,
a siloxane of the formula OSiR63,
a thiolate of the formula SR6,
an acetyl acetonate of the formula (R1CO)2CR6,
a diimine of the formula (R1N=CR6)2,
a cyclopentadienyl of the formula C5HqR65-q with q for 0, 1, 2, 3, 4, 5,
an indenyl of the formula C9H7-rR6r with r for 0, 1, 2, 3, 4, 5, 6, 7,
a fluorenyl of the formula C13H9-sR6s with s for 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 and
a C1 to C30 alkyl group, a C6 to C10 aryl group, and a C7 to C40 alkylaryl group,
R1 to R5 and R6 stand for a C1-C30 alkyl group, a C6-C10 aryl group, a C7-C40 alkylaryl group, in particular for hydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert.-butyl, phenyl, methylphenyl, cyclohexyl and benzyl,
m and k possess the aforementioned signification.
Quite particularly preferred are fulvene metal complexes of formula (I), in which
M stands for titanium, zirconium, hafnium, vanadium, niobium and tantalum.
A stands for bis(trimethylsilyl)amide, dimethylamide, diethylamide, diisopropylamide, 2,6-di-tert-butyl-4-methyl phenolate, cyclopentadienyl, methylcyclopentadienyl, benzyl-cyclopentadienyl, n-butylcyclopentadienyl, pentamethylcyclo-pentadienyl, tetramethyl-cyclopentadienyl, 2,4,7-trimethylcyclopentadieyl, dimethylcyclopentadienyl, indenyl, 2-methylindenyl, 2-methyl-4,5-benzoindenyl, 2-methyl-4-phenylinidenyl, fluorenyl or 9-methyl-fluorenyl.
The specified formula (I) for the fulvene metal complexes is to be regarded as a formal description of the bonding relationships and represents an example of a structural variant. As is known to the skilled man, the bonding relationships of the metal complex are inter alia dependent on the central atom, on the oxidation state and on the substituents of the fulvene ligand.
There are considered as Lewis acids the co-catalysts known in the field of Ziegler-Natta catalysis such as e.g. compounds of aluminum, magnesium or zinc. Suitable as Lewis acids are in particular trialkylaluminum compounds such as trimethylaluminium, triethylaluminium, triisobutylaluminium, triisoetylaluminium, and in addition dialkylaluminium compounds such as diisobutylaluminium hydride, diisobutylaluminium fluoride and diethylaluminium chloride, and also substituted triaryl-aluminium compounds, such as tris(pentafluorophenyl) aluminium as well as ionic compounds which contain as anion tetrakis(pentafluorophenyl)aluminate, such as triphenyl-methyl-tetrakis(pentafluorophenyl) aluminate, as well as N,N-dimethylanilinium-tetrakis-(pentafluorophenyl) aluminate. Further examples of suitable Lewis acids are dialkyl compounds of zinc or magnesium, such as dimethyl zinc, diethyl zinc, diisobutyl zinc, butylethyl magnesium, dibutyl magnesium, as well as dihexyl magnesium.
It is naturally possible to use the co-catalysts in a mixture with each other.
The present invention further provides the use of the novel catalyst system for the polymerisation of unsaturated compounds, in particular of olefins and dienes. By polymerisation is understood both the homo- and the copolymerisation of the above-mentioned unsaturated compounds. In particular use is made for the polymerisation of C2-C10 alkenes, such as ethylene, propylene, 1-butene, 1-pentene and 1-hexene, 1-octene, isobutylene and arylalkenes, such as styrene. There are used as dienes in particular: conjugated dienes, such as 1,3-butadiene, isoprene, 1,3-pentadiene, and non-conjugated dienes, such as 1,4-hexadiene, 1,5-heptadiene, 5,7-dimethyl-1,6-octadiene, 4-vinyl-1-cyclohexene, 5-ethylidene-2-norbornene, 5-vinyl-2-norbornene and dicyclopentadiene.
The catalysts according to the invention are suitable for the production of rubbers based on copolymers of ethylene with one or more of the above-mentioned xcex1-olefins and the above-mentioned dienes. In addition, the catalyst system according to the invention is suitable for the polymerisation of cycloolefins such as norbornene, cyclopentene, cyclohexene, cyclooctane, and the copolymerisation of cycloolefins with ethylene or xcex1-olefins.
The polymerisation can be carried out in liquid phase, in the presence or absence of an inert solvent, or in the gas phase. As solvents are suitable aromatic hydrocarbons, such as benzene and/or toluene, or aliphatic hydrocarbons, such as propane, hexane, heptane, octane, isobutane, cyclohexane or mixtures of the various hydrocarbons.
It is possible to use the catalyst system according to the invention applied to a support. There can be mentioned as suitable support materials e.g.: inorganic or organic polymeric supports, such as silica gel, zeolites, carbon black, activated carbon, aluminium oxide, polystyrene and polypropylene.
The catalyst system according to the invention can further be applied to the support materials in a conventional manner. Methods for the supporting of catalyst systems are for example described in U.S. Pat. 4,808,561, 4,912,075, 5,008,228 and 4,914,253.
The polymerisation is carried out in general at pressures of 1 to 1000, preferably 1 to 100 bar, and temperatures of xe2x88x92100 to +250xc2x0 C., preferably 0 to +150xc2x0 C. The polymerisation can be carried out in conventional reactors, continuously or discontinuously.